Should the sample cassette be placed completely on the outside of all
blasting gear, or can the sample be placed inside a hood but outside of any respiratory
protection?

The correct placement for air sampling cassettes is near the breathing zone of the employee.
It should be as close as possible to the employee's nose and mouth, i.e., in a hemisphere
forward of the shoulders within a radius of 6 to 9 inches. Since OSHA is concerned with an
employee's potential exposure, the cassette must also be located
outside of any protective equipment.

This measurement will, in large part, determine the actions the employer must take to provide
the employee with protection, such as appropriate personal protective equipment, medical
monitoring, and hygiene facilities. Each of the standards you mentioned
(Cadmium, Lead-in-Construction, and Arsenic) recognize ingestion as a route of exposure.
Particles which are too large to contribute to the employee's airborne exposure nevertheless
contribute to the overall exposure through the potential for ingestion. The standards were
written to include protection from ingestion of these toxic metals.

Therefore, while it is true that sampling inside the hood would eliminate particles driven
into the cassette by the force of the blasting operation, it would also result in a
measurement which is not representative of the employee's potential exposure. Measuring
inside the shroud would create an artificially low exposure concentration as it would be
composed of a mixture of the air passing out of the respirator and the contaminated air
outside the hood.

Given the results of the NIOSH Health Hazard Evaluation (HHE)
Report 94-0122-2578, Bath Iron Works Corporation, is the current sampling method acceptable
to OSHA for compliance monitoring?

The current, acceptable sampling method for determining employee exposure is to place the
sampling cassette outside of all personal protective equipment.

The HHE looked at the effect of blasting materials, specifically steel grit, on employee
sampling results. It concluded that non-inhaleable particles of steel grit trapped in the
cassette inflate the employee's airborne lead-exposure level. The study did not determine an
effective method of sampling which would overcome this problem.

Has OSHA conducted any research to determine if the current monitoring
method will meet the accuracy levels specified in the lead, cadmium, and arsenic
regulations?

The monitoring methods OSHA uses for lead, cadmium, and arsenic meet the accuracy
requirements as stated in the standards. The overall accuracy for monitoring, which is
conducted in the field and analyzed in a laboratory, is customarily broken into two
constituents: sampling and analytical error. The analytical error is derived from both the
recovery efficiency of the compound from the collection substrate and the precision of the
analytical technique. Conventionally, the sampling error is plus-or-minus five percent to
account for variations in pump flow. Both of these errors are summed to derive the accuracy
of the method of monitoring. The collection efficiency of the sampler, in this case a 37mm
closed face cassette containing a mixed cellulose ester filter, is assumed to represent the
exposure of interest. There is specific information on analytical and sampling procedures
listed by subject on the OSHA web site in the Chemical Information File, the OSHA Technical
Manual, and the Analytical Methods.

Please describe the specific sampling procedure used by OSHA Compliance
Officers during inspections of blasting operations.

The sampling procedure followed by OSHA Compliance Officers is to place the cassette outside
of all personal protective equipment. Further information is described in OSHA's Technical
Manual, TED 1.15, Section 1, Chapter 1, a copy of which is enclosed for your convenience.

Have any alternative methods or sampling modifications been developed
or considered by OSHA? If so, please provide details.

OSHA adopted its current particulate methodology based upon a general consensus at the time.
The Agency is aware of the continuing discussion of the particle-size-dependent efficiency of
the different sampling devices and of the human body at inhalation or ingestion. The Agency's
Salt Lake Technical Center is closely following the efforts to reach a consensus of which
sampler configuration best represents the exposure of occupational concern.

Would use of a deflector such as that used by NIOSH be acceptable to
OSHA as a means of reducing the likelihood of collecting non-inhaleable particulate?

The effects of simply putting a deflector of unknown specifications at the opening of a
sampling train are not well studied. NIOSH's HHE Report 94-0122-2578 used a deflector and
found the device to be ineffective at shielding the sampler from abrasive blast grit. One
sampler manufacturer has recently introduced a sampler with an inlet port shield by a
perforated screen. The effect of this screen on sampler efficiency is currently being studied
by NIOSH. The use of any deflectors or screens would be evaluated by the Agency based upon
the available information supporting the sampling characteristics of such devices.

Assuming the sample inlet is required to remain outside of all
protective equipment, would OSHA cite an employer for failure to monitor if the employer's
data was generated with the sampling inlet located inside of respiratory protection? Would
your answer be the same if the sampling inlet was located inside a shroud/hood but outside of
respiratory protection?

The employee's potential exposure is the contaminant air concentration in the employee's
personal breathing zone without regard to personal protective equipment, including the
respirator and its abrasive blasting shroud. If the sampling inlet is not located outside of
all personal protective equipment, OSHA could cite the employer for failing to adequately
assess employee exposure.

We hope that this adequately answers your questions. If further information is needed,
please do not hesitate to contact the Office of Health Compliance Assistance on
202-693-2190.

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